Raman spectroscopic studies of the thermal decomposition mechanism of ammonium metavanadate

Abstract

Thermal decomposition of NH₄VO₃ under N₂ and NH₃+ H₂O has been studied on a molecular level by in situ Raman spectroscopy in the temperature range 150–400 °C. Under N₂ , the decomposition mechanism leading to formation of V₂O₅ has been observed to proceed via two intermediates: viz. an amorphous, transitional (NH₄)₂V₄O₁₁ and NH₄V₃O₈ . Under NH₃+H₂O, a slightly different decomposition pathway, rationalized in terms of stability of intermediates, leading to the formation of V₂O₃ has been observed. The identification of Raman-inactive V₂O₃ is further supported by the formation of V₂O₄and V₂O₅ , along with monomeric vanadyl species, through oxidation of V₂O₃ at 400 °C.